Depends on the game. I know there are some people with tons of trophies, but they play a lot of indies to amp that count up. They might only play 2 hours a day, yet to an average person look like a truly hardcore player.
For me, I sometimes play for an hour a day or I am marathonning a really fun game with 10 hours straight. I have 3 or 4 platinums, and they were really long platinums. But the only reason I did it, is because the platinum looked fun. If the platinum sucks to get, then I simply won't do it.
As I said earlier depends on the game, but also the trophies. For some games I just beat the game once and I am done, but for others I play for a very long time.